The hypothesis that this study attempts to test is that expanded peer- mediated interventions for children's developmental skills and achievement will be more effective than techniques which represent the best of current practice. We will recruit approximately 35 to 40 preschoolers with autism enrolled in two integrated classrooms currently funded by the US Department of Education and the National Institute of Mental Health. Youngsters in one classroom will receive expanded peer-mediated interventions for a wide range of skills including cognitive, fine and gross motor, social interaction, language, and appropriate participation in ongoing activities. All interventions will be derivatives of peer cooperation, peer imitation or peer confederate procedures developed by our own and other research groups over the past ten years. Youngsters with autism in the comparison LEAP classroom will receive their standard curriculum, which represents the best current practice available for preschoolers with autism. We will use a wide variety of standardized, curriculum-based, and behavioral observation measures to evaluate children's achievement in this five-year project. It is expected that children receiving expanded peer- mediated interventions will demonstrate superior skill acquisition and development on all outcomes.